John makes it very clear, that we will know who we are when we see Jesus "As He Is."
How is He?
The next verse gives us insight:
"And every man that hath this hope in him purifieth himself, even as he is pure." (1 John 3: 3)
We have this hope, that we will be like Jesus, fully vested in His standing, His being, and His presence.
From the moment that we believe on Jesus, we are taken out of ourselves and brought into Himself:
"And all things are of God, who hath reconciled us to himself by Jesus Christ, and hath given to us the ministry of reconciliation;" (2 Corinthians 5: 18)
"But God, who is rich in mercy, for his great love wherewith he loved us, 5Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) 6And hath raised usup together, and made us sit together in heavenly places in Christ Jesus:" (Ephesians 2: 4-6)
Notice that we are seated with Him - we are in Him:
"To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory: 28Whom we preach, warning every man, and teaching every man in all wisdom; that we may present every man perfect in Christ Jesus: 29Whereunto I also labour, striving according to his working, which worketh in me mightily." (Colossians 1: 27-29)
So, Jesus is pure, and the more that we rest in the truth that we will be like Him, we purify ourselves all the more.